With the rapid development of the network communications technology, new technologies, typically as the packet switching, continuously emerge and develop. The conception, architecture and operating mode of conventional telecommunication networks are dramatically changing. Compared with the conventional circuit switching, due to the incomparable advantages of low cost and high-bandwidth, the packet switching technology can support not only the data traffics, but also TDM voice, data, Asynchronous Transfer Mode/Internet Protocol (ATM/IP) and images. Further, it can perform the conventional circuit switching function, such as Voice over IP (VOIP) technology, etc. Moreover, with the continuous enhancement of the quality of transmitting voice of the packet switching network, the mixture of voice traffics and data traffics, i.e. the mixture of conventional TDM-based circuit switching networks and packet switching-based packet switching data networks has become one tendency of the future network development.
The method of packet switching-based TDM data transport in the relevant art includes the steps of: simultaneously setting up a TDM data interface and a general package data interface in a packet switching device, processing the received TDM data by using the same way as the general package data being processed, i.e. performing a layer-to-layer encapsulation on the received TDM data flow by using the mode defined in the existing protocols. The detailed encapsulated protocol layers are shown in FIG. 1, including a series of protocols with different formats such as Ethernet/ATM protocol, IP protocol, Transmission Control Protocol (TCP) or User Datagram Protocol (UDP), Real-Time Protocol (RTP) and Real-Time Control Protocol (RTCP). Encapsulated by above method, the format of the TDM traffic data may be converted to the data package format. The received data package is converged and bore in the corresponding protocol data unit for transport.
However, as the above solution is mainly proposed to solve the problem of the packet-based TDM data transport in the whole network, i.e. to solve problems such as the layer2 switching of TDM data, the network routing, the data classification on the transport layer, the real-time, etc., multilayer encapsulation is needed to be performed on the TDM data flow in accordance with the existing network protocols. With respect to the connection with shared transmission media, the problems of the port switching, the layer2 switching, and the network routing are absent. Thus the layer3 routing protocol and the real-time protocol are not needed to support the connection. Hence, if the described solution is adopted in such a case, many problems will be brought to the data transport. As the TDM data flow is encapsulated to multilayer and each layer of which is appended an encapsulating header with determined bytes, for example, as a result of which, the ratio of the data payload in the whole data package may be very low, thereby decreasing the effective bandwidth utilization and the transport efficiency. Taken the 802.16 protocol of wireless access network as an example, the Ethernet protocol is used to encapsulate the 2nd layer while the IPv4 is used to encapsulate the 3rd layer. The conventional TDM voice bandwidth is 64 Kbps, thus if one TDM data frame is sent per 20 ms, 160 bytes of TDM data is sent per 20 ms. The encapsulation of each TDM data frame is shown in FIG. 2, and the encapsulation method includes: adding an RTP header of 12 bytes to the data payload in an RTP packing, adding a (user datagram protocol) UDP header of 8 bytes in a UDP packing, adding an IPv4 header of 20 bytes in an IPv4 packing, adding a MAC header of 12 bytes in an Ethernet frame packing and adding a generic MAC header of 6 bytes when forming a 802.16 (protocol data unit) PDU. Furthermore, a check-tail of 4 bytes is appended to the above Cyclic Redundancy Check (CRC) 32 and FCS32 of the 2nd layer and the 3rd layer, respectively. The overall headers, tails and other information except for the data payload are up to 66 bytes. Thus the ratio of the data payload in the whole PDU, i.e. the effective bandwidth utilization, is only
            160              160        +        66              ×    100    ⁢    %    ≈      70    ⁢    %  
In addition, as the solution needs to determine the adapted header format for the TDM data in each layer by table look-up and needs to perform the corresponding header adaptation, multiple times of table look-up and header edition operation are needed. The gateway devices or the corresponding processing modules are further needed and thus increasing the processing load of devices.